Fabrication of Ultraviolet Photodetector Based on ZnO Nanostructures and Calcium Impurities Using Sol-Gel Method

In this paper an ultraviolet (UV) photodetector has been fabricated using ZnO nanostructures. The cheap fabrication process, high-quality nanostructures and the desired results for the photodetector are the most important characteristics of the proposed method. ZnO nanostructures have been grown using sol-gel method. In order to increase the sensitivity, calcium impurities have been added to nanostructures. XRD results show that the obtained nanostructures are free from any unwanted impurities and phases. SEM images show that by adding Ca impurities the dimensions of the nanostructures have been reduced. EDS spectra illustrates that the Ca element exists in the nanostructures. In order to study the optical properties of the grown nanostructures, photoluminescence (PL) spectroscopy has been performed. PL results show that by increasing the impurity the bandgap has been slightly decreased. Raman spectroscopy and the XRD results depict that by increasing the impurity concentration the crystallization of the nanostructures would be reduced. The results for the UV sensor transient photocurrent measurement show that when exposed to light the current is much larger than the dark current, the sensor has a good sensitivity and adding Ca impurities increases the sensitivity considerably.